Experimental study on spectra of femtosecond-laser-induced low-pressure Ni plasma

The spectra of Ni plasma induced by femtosecond laser pulses at sub-atmospheric pressure environment have been studied experimentally in air and argon gas, respectively. The results show that the spectra of laser-induced plasmas are composed of continuous spectra and atomic line spectra in these two surrounding gases. The spectra at lower surrounding pressure show higher resolution due to the decrease of electron density, compared to that at higher pressure. Besides, the intensity of line spectra undergoes the transition from slow increase to rapid decrease. Additionally, the effect of the composition of the surrounding gas on the intensity is also briefly discussed.